Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $59.91   5.376%   $63.1308   $63.13   $63.15   $63.10  
  Purchase #2 $249.57   5.217%   $262.5901   $262.59   $262.60   $262.60  
  Purchase #3 $191.90   8.333%   $207.891   $207.89   $207.90   $207.90  
  Purchase #4 $46.39   3.599%   $48.0596   $48.06   $48.05   $48.10  
  Purchase #5 $37.54   10.804%   $41.5958   $41.60   $41.60   $41.60  
  Purchase #6 $102.41   11.501%   $114.1882   $114.19   $114.20   $114.20  
  Purchase #7 $185.33   3.731%   $192.2447   $192.24   $192.25   $192.20  
  7 purchase totals = $873.05       $929.7002   $929.70   $929.75   $929.70